Question

if n(A)=20,n(B)=30,n(A interset B)=10,find n(A union B)

Answer 1

n ( A union B) = n (A) + n ( B)
= 20+30
=50

Answer 2

we know that n (A union B) = n ( A) +n( B) -n (A intersect B)
》 》 =20 +30 -10
=50-10
=40
so n ( A union B) is 40